Convex Cathode Ion Beam Source for Semiconductor Implantation
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Solution Overview
Problem
As semiconductor wafers increase in size, maintaining within-wafer uniformity (WiWU) becomes more challenging due to the difficulty in achieving precise and uniform ion implantation across larger surfaces, leading to inefficiencies in ion beam distribution and extended equipment lifespan.
Innovation Solution
The ion beam source apparatus features a cathode with a convex front surface and a refractory metal filament, generating secondary electrons that collide with dopant gases to produce plasma, enhancing ionization uniformity and efficiency within the ionization chamber, and includes a repeller and magnetic field to optimize electron paths for improved ion beam generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If semiconductor wafers increase in size to improve throughput and reduce cost per die, then wafer area increases by 125%, but within-wafer uniformity becomes more difficult to maintain
Solution Approach 1:
The patent applies local quality by creating non-uniform electron density distributions through specifically positioned filaments and cathode configurations. Different regions of the ionization chamber receive different electron fluxes, enabling localized ionization that compensates for geometric effects and achieves uniform ion beam distribution across the entire large wafer surface.
Solution Approach 2:
The patent introduces spatial dimensionality control through three-dimensional filament arrangements and cathode surface curvature design. By manipulating electron generation in multiple spatial dimensions, the system achieves uniform ionization across the wafer surface, transforming a two-dimensional uniformity problem into a three-dimensional spatial control solution.
2Productivity
If traditional ion beam sources are used on large wafers, then ion beam distribution becomes inefficient, but equipment lifespan is extended
Solution Approach 1:
The patent changes key parameters including electron generation rate, electron energy distribution, and spatial distribution of ionization sources. By adjusting filament currents, cathode potentials, and geometric configurations, the system optimizes ionization efficiency to improve ion beam distribution while reducing operational stress on components, thereby extending equipment lifespan.
3Manufacturing precision
If more energy is applied to ion beam generation on larger wafers, then ionization efficiency improves, but work needed for ion beam generation increases
Solution Approach 1:
The patent implements continuous useful action through sustained electron emission from multiple filaments and cathodes that work simultaneously across different chamber regions. This continuous ionization process maintains uniform ion beam generation without requiring energy-intensive pulsed operation or repeated adjustments, reducing total work input while preserving ionization uniformity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration results in higher ionization uniformity across all directions, reducing the work needed for ion beam generation by 15% and extending the equipment's lifetime by approximately 50% compared to traditional designs.
Implementation Method 1
at least one filament configured to generate electrons upon heating
Implementation Method 2
a cathode having a front surface and a back surface, and configured to emit secondary electrons from the front surface when the electrons from the at least one filament hit the back surface of the cathode
Implementation Method 3
and includes a repeller and magnetic field to optimize electron paths for improved ion beam generation
Data Source
AI summary
An apparatus includes an ionization chamber and an electron source device at least partially disposed inside the ionization chamber. The ionization chamber is configured to receive at least one chemical and provide plasma having ionized chemicals. The electron source device includes at least one filament configured to generate electrons, and a cathode configured to emit secondary electrons from the front surface when the electrons from the at least one filament hit the back surface of the cathode. The front surface of the cathode is shaped convex facing inside the ionization chamber.